Oil prices reversed earlier gains on Thursday following a rise in U.S. stockpiles but look set to post their first weekly rise in three weeks after the battered market took heart from a tentative deal by major producers to freeze output at January's highs.

Still, doubts about how much other countries will cooperate have weighed on investors, with the focus squarely on Iran, which has pledged to increase output sharply to regain market share lost when sanctions were in place.

Brent crude LCOc1 extended losses on Friday, and was last trading down 0.9 percent at $33.99 per barrel, but is up 1.9 percent for the week.

U.S. crude was at $30.53 CLc1, off a two-week high of $31.98 hit on Thursday but up 3.7 percent so far this week.

"I would assume oil prices will face downward pressure and there will be selling into a rally," said Daisuke Uno, chief strategist at Sumitomo Mitsui Bank.

In a sign that investor fears over a global economic slowdown are far from being on the wane, traditional safe-haven assets held firm after a strong outperformance on Thursday.

Gold XAU= surged 1.8 percent on Thursday to $1,230.90 per ounce and last stood at $1,226.56.

Investors also flocked to the safety of top-rated government bonds, with the 10-year U.S. Treasuries yield US10YT=RR falling back to 1.7294 percent, compared with Wednesday's one-week high of 1.8470 percent.

In the currency market, the yen regained its edge, rising to 113.13 per dollar JPY= from this week's low of 114.875.

The euro fell to as low as 125.34 yen EURJPY= on Friday, a low last seen in June 2013, and last traded at 125.83 yen.

Against the dollar, the common currency EUR= traded at $1.1124, having slipped to a two-week low of $1.1071 on Thursday.

The minutes from the European Central Bank's January meeting showed some policymakers are advocating the need to act pre-emptively in the face of new threats on the economy.

A big focus is on the British pound and the EU summit in Brussels, where UK Prime Minister David Cameron is seeking more favorable terms for its EU membership.

A successful deal there is expected to lead to a referendum on EU membership as soon as in June.

"We expect a correction lower in EURGBP should an agreement be reached at the meeting, although an impasse, to which we assign a non-negligible probability, would likely weigh on the GBP," wrote Barclays analysts in a report.

The pound stood at $1.4333 GBP=D4, having fallen to a near seven-year low of $1.4080 last month partly on worries about so-called "Brexit".

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